The present invention relates to a parenteral apparatus.
Injection devices which use a sharp needle to enter human tissue are now widely recognized as being hazardous to users and other individuals because the sharp point, contaminated by its exposure to the tissue of the first person may penetrate the skin of a second person and in doing so may carry micro-organisms from the patient on whom the injection device was first used into the tissue of a second person. Such transmission may result in the development of disease in the second person. When the penetration of the skin is accidental it is referred to as xe2x80x9cneedlestick injuryxe2x80x9d or xe2x80x9cneedleprick injuryxe2x80x9d.
Disease transmission by this means is now recognised as a major cause of occupational disease transmission to healthcare workers. The prevention of such transmission has resulted in the setting up of expensive and inefficient procedures and has caused an increase in the cost of providing medical support.
Transmission of disease may also result from the deliberate re-use of a sharp needle by a second person and this is a major cause of transmission of such diseases as hepatitis C and AIDS (HIV) amongst users of narcotic intravenous drugs. Many other infectious diseases may be transmitted from one person to another by contaminated needles.
Three main strategies have been put in place to reduce the risk of disease transmission by contaminated needles. These are
(i) strict adherence to methods and procedures which reduce the risk of accidental needlestick injury;
(ii) the widespread distribution of secure containers (sharps containers) into which the used needles can be placed as soon as possible after use; and
(iii) the invention and development of injection devices whereby the sharp needle point can be covered soon after use, so reducing the risk of needlestick injury, and in many examples, reducing the possibility of the injection device being used a second time.
A disadvantage of all of these strategies is that they all cause some perturbation of optimal or most efficient clinical practice and all incur increased expense in providing medical care. Often these factors mean that the safety measures fail not because the device does not provide safety but simply because they are not put into universal practice. Most importantly, these strategies and techniques leave a xe2x80x9cwindow of riskxe2x80x9d in the interval between removing the contaminated needle from the tissue of a person and putting into effect the chosen procedure or technique to make the contaminated needle safe.
There is a second type of problem associated with the use of sharp tubular needles to obtain access to living tissues, especially veins or arteries. This second problem is that the sharp point is only necessary to advance the needle to the required location in the tissue. When in the desired location the sharp point is often a disadvantage.
The prior art also shows a great variety of methods of covering a sharp needle tip, such as a sheath moving forward to cover the needle after use, retraction of the needle into the body of the syringe or capture of the hub of the needle by a latch on the moving plunger after emptying the syringe. These methods are associated with varying degrees of complexity and interference with normal clinical requirements. Above all they do not allow the use of the device for the transfer of fluid to or from the living tissue after the sharp tip is covered and do not protect the living tissue from damage by the sharp tip during the parenteral procedure. An internal blunt tube within the sharp tubular needle overcomes many of these problems to a degree but has the disadvantages of significantly increasing the resistance to fluid flow and of not permitting the sharp needle point to be covered.
It is an object of the present invention to provide an apparatus which can be used in much the same way as conventional tubular injection needles and catheters for achieving fluid transfer between the exterior and the parenteral tissue of the living body and without requiring difficult or complex techniques to maintain fluid transfer passages during movement of the needle within the device.
In accordance with one aspect of the present invention there is provided a parenteral apparatus characterised by a housing having a first end and a second end and defining a chamber for parenteral fluid, a thin walled catheter having a free end closely enclosing a tubular needle having a sharp point, the catheter being mounted to the housing, the needle and the catheter being longitudinally moveable relative to one another between a first position at which the needle extends from the catheter so that the sharp point is exposed and a second position at which the sharp point is located within the housing, the needle remaining in a fluid pathway of the parenteral apparatus at all times between the first and second positions, the sharp point of the needle being arranged to pierce tissue when the catheter and the needle are in their relative first position and retraction means being provided for moving the needle and catheter relatively from the first position.